Unsaturated hydrocarbons such as ethylene and propylene are often employed as feedstocks in preparing value added chemicals and polymers. Unsaturated hydrocarbons can be produced by pyrolysis or cracking of hydrocarbons including hydrocarbons derived from coal, oil, gas, synthetic crude, naphthas, natural gas liquids, raffinate, refinery gases, ethane, propane, butane, and the like. Unsaturated hydrocarbons products produced in these manners usually contain highly unsaturated hydrocarbons such as acetylenes and diolefins that adversely affect the production of subsequent chemicals and polymers. Thus, to form an unsaturated hydrocarbon product such as a polymer grade monoolefin, the amount of acetylenes and diolefins in the monoolefin stream is typically reduced.
One technique commonly used to reduce the amount of acetylenes and diolefins in an unsaturated hydrocarbon stream primarily comprising monoolefins involves hydrogenating the acetylenes and diolefins to monoolefins. This process is selective in that hydrogenation of a monoolefin and a highly unsaturated hydrocarbon to the saturated hydrocarbon is minimized. For example, the hydrogenation of ethylene or acetylene to ethane is minimized.
One challenge to the selective hydrogenation process is the potential for a runaway reaction which is uncontrolled hydrogenation of ethylene to ethane. One methodology to minimize runaway reactions is to use a highly selective hydrogenation catalyst. The availability of highly selective hydrogenation catalysts, however, has brought about other challenges for converting a highly unsaturated hydrocarbon to an unsaturated hydrocarbon.